System for positioning on a patient an observation and/or intervention device

ABSTRACT

The present invention relates to a system for positioning with respect to a patient&#39;s body an observation and/or intervention device having a portion penetrating into the patient&#39;s body comprising a base laid on the patient&#39;s body; a means for supporting the device formed of a first portion movably assembled on the base according to a connection with one degree of freedom, and of a second portion movably assembled on the first portion according to a connection with one degree of freedom and connected to the device; and means for actuating the first portion with respect to the base, and the second portion with respect to the first portion, in which the base surrounds at a distance at least partially the device, said device being detachably connected to the second portion to enable removal of the positioning system while leaving in place the device.

The present invention relates to a system for positioning on a patientan observation and/or intervention device having a portion penetratinginto the patient's body. It for example applies to medical analysissystems, such as endoscopic systems, and it will more specifically bedescribed in the case of a use of an endoscope in a laparoscopy.

In such a type of operation, an endoscope formed of a thin optical tubeis inserted into the patient's abdomen through a small incisionperformed at the level of the patient's abdomen. The optical tube isgenerally connected to an external video camera. Other incisions may beperformed to introduce surgical instruments handled by a surgeon. Theendoscope is used to visualize the patient's internal organs and thesurgical instruments. Since the surgeon generally has both handsoccupied by the surgical instruments, an assistant is necessary tomaintain the endoscope in a desired position.

Robotic systems have been developed to handle the endoscope instead ofthe assistant. Such systems are generally formed of massive, complex,and expensive robots comprising a base attached to the ground and an armhandling the endoscope. In the limited space of an operation table, thebase of such a robot takes up a considerable place next to the patient.Further, the robot's arm maintaining the endoscope may hinder the accessto the patient's abdomen.

It is thus desirable to provide a system for positioning on a patient anobservation and/or intervention instrument taking up a small volume tolimit the space required in the operation theatre and clear the accessto the patient as much as possible.

International patent application WO0105319 assigned to the UniversiteJoseph Fourier describes, in an embodiment, a system for positioning anobservation and/or intervention device, for example, an endoscope. Thesystem comprises a mount placed on the patient's body, supporting atrocar in which the observation and/or intervention device slides, thetrocar being likely to pivot with respect to the mount. An actuatorassembly controls the trocar movement with respect to the mount. It maybe formed of pneumatic or hydraulic actuators, each actuator beingdirectly connected to the mount and to the trocar. It may also be formedof cables. Each cable then extends between the trocar and a guideattached on the mount, and is driven at its free end by an actuatorplaced at a distance from the patient.

A disadvantage of such a system is the difficulty to impose significantmovements to the trocar. Indeed, in the case where the actuators areplaced directly on the mount, the volume taken up by the actuatorslimits the trocar movements. In the case where the actuators are placedat a distance from the patient, the trocar movements are obtained by theapplication of tractions of different amplitudes on the cables connectedto the trocar. A difficulty then results, in large movements, from thehigh flexion angles imposed to the cables at the level of the guides.This may result in a fast deterioration of the cables. Further, withsuch a system, the forces exerted by the cables or the actuators on thetrocar are the origin of a pressure exerted by the trocar on thepatient's abdomen that may be undesirable. Another disadvantage of sucha system is that it is generally not possible to remove the positioningsystem while leaving in place the trocar and the observation and/orintervention devices.

The present invention provides a system, taking up a small volume, forpositioning on a patient's body an observation and/or interventiondevice having a portion penetrating into the patient's body, enablingobtaining significant movements of the observation device and enablingremoval of the positioning system while leaving in place the observationand/or intervention device.

The present invention also provides a positioning system limiting theapplication of pressure forces on the patient's abdomen.

To achieve these objects, the present invention provides a system forpositioning with respect to a patient's body an observation and/orintervention device having a portion penetrating into the patient's bodycomprising a base laid on the patient's body; a means for supporting thedevice formed of a first portion movably assembled on the base accordingto a connection with one degree of freedom, and of a second portionmovably assembled on the first portion according to a connection withone degree of freedom and connected to the device; and means foractuating the first portion with respect to the base, and the secondportion with respect to the first portion, in which the base surroundsat a distance at least partially the device and in which the device isdetachably connected to the second portion to enable removal of thepositioning system with respect to the device while leaving in place thedevice with respect to the patient's body.

According to an embodiment of the present invention, the base delimits acircular opening around the device and the first portion is a mobilering with an axis substantially perpendicular to the patient's body andwith an inner diameter substantially corresponding to the circularopening, the mobile ring being rotatably assembled on the base aroundits axis.

According to an embodiment of the present invention, the second portioncomprises a head connected to the device prolonging at least in an armpivotally assembled on the mobile ring along an axis substantiallytangent to the patient's body.

According to an embodiment of the present invention, the first portioncomprises a semi-circular rail having its ends pivotally assembled onthe base along an axis substantially tangent to the patient's body.

According to an embodiment of the present invention, the second portioncomprises a carriage slidably assembled on the rail and connected to thedevice.

According to an embodiment of the present invention, the device ismovably assembled on the second portion according to a connection withone degree of freedom.

According to an embodiment of the present invention, the motions of thefirst and second portions are controlled by cables driven by actuatorslocated at a distance from the patient.

According to an embodiment of the present invention, the rotating motionof the mobile ring with respect to the base is controlled by an actuatorattached to the mobile ring, the actuator extending to be substantiallyparallel to the mobile ring axis.

According to an embodiment of the present invention, the pivoting motionof the arm with respect to the mobile ring is controlled by an actuatorattached to the second portion and extending to be substantiallyparallel to the pivoting axis of the arm with respect to the mobilering.

According to an embodiment of the present invention, the device extendssubstantially longitudinally along a direction perpendicular to thepivoting axis of the arm with respect to the mobile ring and the deviceis movably assembled with respect to the second portion, to slide alongsaid direction, the device sliding with respect to the second portionbeing controlled by an actuator attached to the second portion andextending to be substantially parallel to the pivoting axis of the armwith respect to the mobile ring.

The foregoing objects, features, and advantages, as well as others ofthe present invention will be discussed in detail in the followingnon-limiting description of specific embodiments in connection with theaccompanying drawings, among which:

FIG. 1A shows a perspective view of a first embodiment of a positioningsystem according to the present invention;

FIG. 1B shows a partial top view with a partial cross-section view ofthe system of FIG. 1A;

FIG. 1C shows a partial lateral cross-section view of the system of FIG.1A;

FIG. 2A shows a partial top view with a partial cross-section view of analternative of the system according to the first embodiment;

FIG. 2B shows a partial lateral cross-section view of the system of FIG.2A;

FIG. 3A shows a very simplified side view of a second embodiment of thesystem according to the present invention;

FIG. 3B shows a front view of the system of FIG. 3A;

FIG. 3C shows a top view of the system of FIG. 3A;

FIG. 4A shows a perspective view of an alternative of the firstembodiment of a positioning system according to the present invention;

FIGS. 4B and 4C shows side views of the system of FIG. 4A at twodifferent positions; and

FIG. 4D shows a top view of the system of FIG. 4C.

FIGS. 1A to 1C show a first embodiment of a system 10 for positioning anendoscope 12 placed in a trocar 14, endoscope 12 and trocar 14penetrating into a patient's abdomen through a small incision 16.Endoscope 12 has the aspect of a cylindrical tube of axis Ω of a lengthof some forty centimeters and of a diameter of a few centimeters. InFIG. 1B, a portion only of trocar 14 is shown. In FIG. 1C, only axis Ωof endoscope 12 is shown. A camera, not shown, is attached to the end ofendoscope 12 external to the abdomen.

System 10 comprises a substantially planar base 18 comprising a planarring-shaped central portion 20, surrounding incision 16, from which fourarms 21 extend. A cylindrical opening 22 is formed at the end of eacharm 21. Openings 22 may be used to maintain base 18 on the patient'sbody via straps, cables, etc. attached to the table on which the patientis laid or directly attached to the patient. Base 18 may also be gluedon the patient's abdomen.

Central annular portion 20 supports a mobile ring 24 of axis Δsubstantially perpendicularly to the plane tangent to the abdomen at thelevel of incision 16. Mobile ring 24 is rotatably assembled around axisΔ on central portion 20 via a bearing 25.

A stirrup 26 is pivotally assembled on mobile ring 24 according to anaxis Γ substantially perpendicular to axis Δ, and substantiallycomprised in the plane tangent to the abdomen at the level of incision16. Stirrup 26 comprises a head 28 on which is attached trocar 14 by anyknown attachment means, which enables simple and fast connection andseparation of trocar 14 and of head 28. Said means will for example beflexible tongues 27. The inner diameters of mobile ring 24 and ofring-shaped central portion 20 are selected to enable removal of system10 during an intervention without displacing trocar 14, or to enableremoval of trocar 14 from the patient's abdomen without displacingsystem 10. Head 28 prolongs in two arms 30, 31, each comprising at oneend a sliding surface 32, corresponding to a cylindrical portion, likelyto slide on a profile 34, 35 shaped as a half-cylinder of axis Γ. Eachprofile 34, 35 moves along with a base 36, 37 attached on ring 24, forexample, by screwing. Each arm 30, 31 comprises at its free end a cap38, 39 (not shown in FIG. 1C) which forms with sliding surface 32 of theassociated arm 30, 31 a housing receiving profile 34, 35.

Mobile ring 24 comprises on its external cylindrical wall a groove 42receiving a cable 43. A guide 44 assembled on base 18 receives the endsof two sheaths 45, 46 in which cable 43 slides. Guide 44 is arranged onbase 18 so that cable 43, as it comes out of one of sheaths 45, 46, istangent to groove 42 of mobile ring 44. The ends of cable 43 areconnected to the ends of a rack (not shown) meshing in with the outputshaft of an electric motor. The displacement of cable 43 by the motorrotates ring 24 with respect to central annular portion 20 around axisΔ.

A pulley sector 47, substantially corresponding to a cylindrical sector,is attached to one of arms 31 of stirrup 26. A groove 48 is formed onthe lateral wall, corresponding to a cylinder portion of pulley sector47. Groove 48 receives two cables 49 and 50, each cable 49, 50 beingattached to an opposite end of groove 48. The other ends of cables 49,50 are connected to the ends of a rack (not shown) meshing in with theoutput shaft of an electric motor. Two supports 51, 52 are attached tomobile ring 24 and each receives the end of a sheath 53, 54 in which oneof cables 49, 50 slides. Supports 51, 52 are arranged so that cables 49,50, as they come out of sheaths 53, 54 are substantially tangent topulley sector 47. When the electric motor displaces the rack, a tractionis exerted on one of cables 49, 50, and a thrust is exerted on the othercable 49, 50. Cables 49, 50 displace pulley sector 47 and, accordingly,stirrup 26. The sliding surfaces 32 of arms 30, 31 then slide onprofiles 34, 35 so that stirrup 26 generally pivots with respect to axisΓ.

Endoscope 12 is assembled to freely slide along axis Ω in trocar 14. Ahold element 55 is attached to endoscope 12. A compression spring 56bears at one end against hold element 55 and at the opposite end againsttrocar 14. A cable 57 is connected at one end to hold element 55 and atits opposite end to a rack (not shown) meshing in with the output shaftof an electric motor. A guide 58 attached on head 28 of stirrup 26receives the end of a protection sheath 59 in which cable 57 slides. Atraction on cable 57 makes endoscope 12 slide in trocar 14 along axis Ωand compresses spring 56. When cable 57 is released, spring 56 relaxesand brings endoscope 12 back to an idle position. Hold element 55 caneasily be removed from endoscope 12 to enable removal of endoscope 12from trocar 14, for example, to clean its lens, or to replace it withanother endoscope having a different length or viewing cone.

The three motors and the racks are for example arranged in a packagedistant from the patient. The motor control may be performed in anyknown fashion and will not be detailed hereafter. It may for example bea vocal control, a manual control by lever or buttons, a foot control,etc. The motor control may be performed in open or closed loop. Forexample, system 10 may also comprise a location means to detect theposition and the orientation of incision 16, of endoscope 12, and of anintervention instrument handled by the surgeon. The location means maybe connected to a calculator capable of controlling motors. Theendoscope is then displaced to, for example, transmit an imagepermanently following the end of the intervention instrument.

The motors are preferably clutch releasable to enable the surgeon tomanually displace positioning system 10.

Cables 43, 57 and cable assembly 49, 50 each control a degree of freedomof endoscope 12. Cables 43, 49, 50, 57 are arranged not to undergosignificant flexion angles. In particular, pulley sector 47 has asufficiently large radius, preferably greater than 50 mm, to limit thecurvature of cables 49, 50. This enables preventing fast deteriorationof cables 43, 49, 50, 57.

Base 18 and stirrup 26 may be made of steel to increase their durabilityand ease their sterilization. Cables 43, 49, 50, 57 may be formed of amaterial covered with Teflon and placed in Teflon sheaths 45, 46, 53,54, 59.

FIGS. 2A and 2B are similar, respectively, to FIGS. 1B and 1C and showan alternative of positioning system 10 according to the firstembodiment. Only the differences with respect to the first embodimentwill be described.

According to this alternative, the electric motors driving the actuatingcables are directly arranged at the level of positioning system 10. Themotors are arranged to hinder as little as possible the movements ofendoscope 12. For example, a first motor 60, comprising a cylindricalpackage 61 and an output shaft 62, is assembled on a support 63connected to base 18 so that output shaft 62 substantially extends alongan axis parallel to axis Δ. Output shaft 62 rotates a pulley 64. Pulley64 is connected to mobile ring 24 by a cable 65 to drive mobile ring 24similarly to the first embodiment.

A second motor 66, comprising a cylindrical package 67 and an outputshaft 68, is assembled on a support 69 connected to mobile ring 24 sothat output shaft 68 extends substantially along an axis perpendicularto axes Δ and Ω. Output shaft 68 rotates a pulley 70. Pulley 70 isconnected to pulley sector 47 by a cable 71 to drive pulley sector 47similarly to the first embodiment. The supply and control means ofmotors 60, 66 are not shown. Motors 60 and 66 may be controlled by anyconventional device. In particular, packages 61, 67 may comprise supplymeans and remote-control means. The sliding of endoscope 12 in trocar 14may also be controlled by a third motor (not shown) directly placed atthe level of hold element 55.

The present alternative of the first embodiment enables completelyfreeing the patient's abdomen during the surgical intervention.

FIGS. 3A to 3C very schematically show a second embodiment of system 10for positioning trocar 14 in which the endoscope (not shown) slides, thetrocar and the endoscope penetrating into the patient's abdomen throughincision 89.

According to the second embodiment, system 10 comprises a “C”-shapedbase 80 resting on the patient's abdomen. A semi-circular rail 82 ispivotally assembled on base 80 around an axis substantially tangent tothe patient's abdomen. The two ends of rail 82 are substantiallyconnected to the two ends of base 80 by two pivotal connections 84, 86.A carriage 88 is slidably assembled on rail 82. Carriage 88 supportstrocar 14.

The means for controlling the sliding of the endoscope in trocar 14 arenot shown in FIGS. 3A to 3C and may be identical to those of the firstembodiment.

The sliding of carriage 88 on rail 82, and the pivoting of rail 82 withrespect to base 80, may be controlled by cable driven by actuatorsplaced at a distance from the patient as for the first embodiment, or bydirectly arranging the actuators at the level of positioning system 10as for the previously-described alternative of the first embodiment.

According to an alternative of the present invention, the rotatingmotions of endoscope 12 in trocar 14 around its axis Ω may also becontrolled by an actuator.

According to the second embodiment, the removal of the positioningsystem is eased by the fact that base 80 is “C” shaped.

FIGS. 4A to 4D show views of an alternative of positioning system 10according to the first embodiment. In FIGS. 4A to 4D, the incision madeon the patient for the placing of endoscope 12 has not been shown. InFIGS. 4B to 4D, only axis Ω of endoscope 12 is shown.

According to the present alternative of the first embodiment, trocar 14is maintained on stirrup 26 by a mounting flange 90, for example,screwed on stirrup 26. Trocar 14 comprises a protrusion 92 located onthe side of mounting flange 90 opposite to ring-shaped base 18.Protrusion 92 may represent handles, tightness valves, connectors, etc.A fixed ring 95 is arranged between ring-shaped base 18 and mobile ring24. Fixed ring 95 forms one piece with base 18. Mobile ring 24 isrotatably assembled on fixed ring 95. Fixed ring 95 comprises aperipheral toothing (not shown) on its external lateral surface.

A first electric motor 96, intended to rotate mobile ring 24 withrespect to fixed ring 95, is assembled to move along with mobile ring 24via a stage 98. First motor 96 is controlled and supplied by means notshown, for example, by electric wires. A toothed wheel 100 is arrangedat the end of shaft 102 of first motor 96. Shaft 102 is substantiallyparallel to axis A of mobile ring 24. Toothed wheel 100 meshes in withthe toothing of fixed ring 95. Since toothed wheel 100 cooperates withfixed ring 95, the rotating of toothed wheel 100 by first motor 96rotates mobile ring 24 with respect to fixed ring 95. Motor 96 movesalong with mobile ring 24 and thus remains fixed with respect to mobilering 24 upon rotation thereof. Upon sole rotation of mobile ring 24,there thus is no risk for trocar 14 and first motor 96 to collide. It isthus possible to pivot mobile ring 24 by more than 360 degrees.

A second electric motor 104 is attached to stirrup 26, on the side ofstirrup 26 opposite to mounting flange 90, via a stage 106. The shaft(not visible in the drawings) of second motor 104 is oriented alongpivoting axis Γ of stirrup 26. Stage 106 comprises an opening (notvisible in the drawings) enabling passing of the shaft of second motor104. Second motor 104 is controlled and supplied by means not shown, forexample, electric wires. A drive element 108 comprises a circular arc109 having its ends connected by a rectilinear portion 110 attached tomobile ring 24. Drive element 108 substantially extends in a planeperpendicular to the plane containing mobile ring 24. The axis ofcircular arc 109 corresponds to pivoting axis Γ of stirrup 26. The wallof circular arc 109 opposite to rectilinear portion 110 comprises atoothing (not shown). The shaft of second motor 104 supports a toothedwheel (not shown) which cooperates with the toothing of circular arc 109so that, when the toothed wheel is rotated by second motor 104, stirrup26 is pivoted with respect to mobile ring 24. The toothing is providedinside of drive element 108 for security reasons and to increase thecompactness of positioning system 10.

The free end of endoscope 12 comprises a cylindrical stop 112 from whicha pin 114 projects. Compression spring 56 bears at one end againstcylindrical stop 112 and at the opposite end against trocar 14. A thirdelectric motor 116 is attached to stirrup 26, next to second motor 104,via a stage 118. Stage 118 comprises an opening 120 enabling passing ofshaft 122 of third motor 116. Shaft 122 of third motor 116 is orientedalong pivoting axis Γ of stirrup 26. Third motor 116 is controlled andsupplied by means not shown, for example, by electric wires. A windingcylinder 124 is arranged at the free end of shaft 122. A helicalthreading (not shown) is formed on the outer surface of winding cylinder124. A cable 125 (only shown in FIG. 4A) is connected at its ends to pin114 and to cylinder 124 and wound around cylinder 124. Third electricmotor 116 is arranged between second motor 104 and protrusion 92 toavoid for cable 125 to contact second motor 104. When third motor 116rotates shaft 122, cable 125, guided by the threading of cylinder 124,winds around cylinder 124 and brings cylindrical stop 112 closer totrocar 14. Endoscope 12 then slides in trocar 14 along axis Ω andcompresses spring 56. When third motor 116 is no longer actuated, spring56 relaxes and brings endoscope 12 back to an idle position. Cylindricalstop 112 may be disassembled from endoscope 12 to enable removal ofendoscope 12 from trocar 14. Cylindrical stop 112 may move along withendoscope 12. The cable end connected to pin 114 can then be detached torelease endoscope 12 from trocar 14. Stages 106, 118 may be directlyintegrated to stirrup 26 and/or be provided on a same side of stirrup26.

The rotating motions of endoscope 12 in trocar 14 around its axis Ω mayalso be controlled by an actuator.

In FIGS. 4A to 4D, ring-shaped base 18 is maintained on the patient viafour curved tongues 126 radially extending from ring-shaped base 18. Asupport arm, oriented by the surgeon before the beginning of theoperation, may be provided to support positioning system 10 and avoidfor the entire weight of positioning system 10 to be applied on thepatient.

A notch 128 is provided at the level of mobile ring 24, substantially indiametrically opposite position with respect to first electric motor 96.Notch 128 is intended to receive a portion of trocar 14 when the latteris inclined to a maximum with respect to ring-shaped base 18, as shownin FIG. 4B. A maximum inclination angle greater than in the absence ofnotch 128 has then been achieved. Notch 128 may be replaced by a hollowprint performed in mobile ring 24 and the shape of which iscomplementary to the shape of trocar 14.

In FIGS. 4C and 4D, trocar 14 is shown as inclined with respect to theplane of ring-shaped base 18 to a position where the second and thirdmotors 104, 116 thrust against first motor 96. Trocar 14 being attachedto stirrup 26 by mounting flange 90 on the side opposite to second andthird motors 104, 106, it can then be easily released from positioningsystem 10. Stirrup 26 being maintained in a thrust position againstfirst motor 96, an obstacle-free region 130 is freed between stirrup 26and ring-shaped base 18, enabling removal of positioning system 10 whileleaving in place trocar 14, the dimensions of the obstacle-free regionbeing sufficient to enable removal of positioning system 10 despite thepresence of protuberance 92 and cylindrical stop 112.

The system according to the present invention has many advantages.

First, the positioning system according to the present invention takesup a small volume, is formed of a relatively simple structure, and has asmall weight. As an example, the applicant has formed a positioningsystem according to the present invention comprised in a cylinder with a70-mm diameter and with a 75-mm height, with a weight approximatelysmaller than 600 g (to which must be added the weights of the endoscope,of the trocar, and possibly of the camera). Several positioning systemsaccording to the present invention may thus be placed simultaneously ona patient's body, each system enabling positioning an observation and/orintervention device.

Second, the pivoting axis of the endoscope with respect to the patient'sbody is substantially tangent to the patient's body, which enablesreducing to a minimum the dimensions of the incision to be performed forthe introduction of the trocar and of the endoscope into the patient'sbody.

Third, the positioning system according to the present invention enablesobtaining movement angle of the endoscope between axes Ω and Δ greaterthan 80°, with a 0.5° accuracy and a pivoting axis on the order of25°/s, and a sliding of endoscope 12 in trocar 14 along axis Ω greaterthan 200 mm, with a 5-mm accuracy and a sliding speed on the order of 25mm/s.

Fourth, the system enables applying no force on the patient's abdomen atthe level of the incision through which the endoscope penetrates intothe abdomen.

Fifth, only three actuators are necessary to control the endoscopedisplacements. This enables simple and accurate control of theactuators.

Sixth, the system according to the present invention may easily bearranged on the patient's body and removed from the patient's body whilemaintaining in place the trocar and the endoscope.

Of course, the present invention is likely to have various alterationsand modifications which will occur to those skilled in the art. Inparticular, the electric motors may be replaced with any type ofactuators. Further, the system according to the present inventionenables positioning devices other than an endoscope. It may be, forexample, a separator, a clip, etc.

1. A system (10) for positioning with respect to a patient's body anobservation and/or intervention device (12, 14) having a portionpenetrating into the patient's body comprising: a base (18, 80) laid onthe patient's body; means for supporting the device formed of a firstportion (24, 82) movably assembled on the base according to a connectionwith one degree of freedom, and of a second portion (26, 88) movablyassembled on the first portion according to a connection with one degreeof freedom and connected to the device; and means (43, 49, 50, 60, 66)for actuating the first portion with respect to the base, and the secondportion with respect to the first portion, characterized in that thebase surrounds at a distance at least partially the device and in thatthe device is detachably connected to the second portion to enableremoval of the positioning system with respect to the device whileleaving in place the device with respect to the patient's body.
 2. Thesystem of claim 1, in which the base (18) delimits a circular openingaround the device (12, 14) and in which the first portion (24) is amobile ring with an axis (Δ) substantially perpendicular to thepatient's body and with an inner diameter substantially corresponding tothe circular opening, the mobile ring being rotatably assembled on thebase (18) around its axis.
 3. The system of claim 2, in which the secondportion (26) comprises a head (90, 28) connected to the device (12, 14)prolonging at least in an arm (30, 31) pivotally assembled on the mobilering (24) along an axis (Γ) substantially tangent to the patient's body.4. The system of claim 1, in which the first portion (82) comprises asemi-circular rail having its ends pivotally assembled on the base (80)along an axis substantially tangent to the patient's body.
 5. The systemof claim 4, in which the second portion (88) comprises a carriageslidably assembled on the rail (82) and connected to the device (12,14).
 6. The system of claim 1, in which the device (12) is movablyassembled on the second portion (28, 88) according to a connection withone degree of freedom.
 7. The system of claim 1, in which the motions ofthe first (24, 82) and second (26, 88) portions are controlled by cables(43, 49, 50) driven by actuators located at a distance from the patient.8. The system of claim 2, in which the rotation motion of the mobilering (24) with respect to the base (18) is controlled by an actuator(96) attached to the mobile ring, the actuator extending to besubstantially parallel to the mobile ring axis (Δ).
 9. The system ofclaim 3, in which the pivoting motion of the arm (30, 31) with respectto the mobile ring (24) is controlled by an actuator (104) attached tothe second portion (26) and extending to be substantially parallel tothe pivoting axis (Γ) of the arm (30, 31) with respect to the mobilering (24).
 10. The system of claim 3, in which the device (12) extendssubstantially longitudinally along a direction perpendicular to thepivoting axis (Γ) of the arm (30, 31) with respect to the mobile ring(24) and in which the device is movably assembled with respect to thesecond portion (26), to slide along said direction, the device slidingwith respect to the second portion being controlled by an actuator (116)attached to the second portion and extending to be substantiallyparallel to the pivoting axis (Γ) of the arm (30, 31) with respect tothe mobile ring (24).